This invention relates to a sensor using a field effect transistor, and more particularly to a sensor having enhanced detecting sensitivity by firmly affixing a sensing material to the gate electrode of a field effective transistor an maintaing the sensing material in an active state.
Sensors using field effect transistors are used as pH sensors, various ion sensors, bio-sensors and others. Referring, for example, to a bio-sensor, bio-sensors conventionally known are prepared by the method of fixing protein or enzyme to the surface of a glass electrode, or the method of fixing a sensing material of protein or enzyme on the gate electrode of a field effect transistor (FET). In such conventional methods, however, the fixing method of enzyme or protein was not satisfactory, and the sensitivity was not so high.
That is, in the conventional protein or enzyme fixing method, the enzyme or protein was directly applied to the FET electrode or glass electrode, the protein or enzyme was mixed in the resin and applied, or fixed to the resin particles and applied, or the protein or enzyme was fixed by way of an organic film.
However, in the direct application method, the protein or enzyme was separated during measurement, and the durability was not sufficient, or in the method of mixing protein into resin and applying or fixing it to resin particles and applying, part of the protein or enzyme was deactivated and the activity was lowered, or in the conventional method of fixing the protein by way of an organic film, the activity was also insufficient.